There exists a need for systems capable of detecting the proximate phase of coolant flow in a reactor core, and for instruments capable of detecting liquid level in the core. United States governmental regulations specify "thermal hydraulic" measurement capabilities in all operating power reactors. These needs and requirements are the result of the TMI accident.
During such an "event" in a pressurized water reactor, there might be a period during which the reactor pressurizer will overfill with water while the primary pumps are operating. The reactor coolant may be in two-phase flow through the coolant loop and might have a significant void fraction. At the present time, the reactor operator has no instrumentation which would indicate a void fraction or liquid level exists in the core. If the pumps are shut off, the void fraction in the coolant will separate, exposing a portion of the core. Because of the unavailability of monitoring systems for either of these conditions, the operators of the reactor may be unaware of these conditions until serious damage results to the core itself.
The present system is designed to provide continuous monitoring of coolant conditions at one or more locations within an operating reactor vessel. It can be used to determine the nominal coolant phase at a designated location.